Liquid biopsies for improving the pre-operative diagnosis of ovarian cancer

In the Netherlands, 7,600 women are diagnosed with an ovarian tumor annually.
Only 5% of these tumors are malignant upon definitive histological assessment.
This means that a general gynecologist encounters a patient with early-stage
ovarian cancer less than once a year. It is, therefore, a challenge to diagnose
preoperative ovarian carcinoma. Accurate preoperative diagnosis is crucial
because patients with ovarian carcinoma need to undergo surgery in an oncology
center, performed by a gynecologic oncologist.

Current preoperative methods to distinguish between benign and malignant
ovarian tumors are based on classification systems containing clinical,
biochemical, and ultrasound features. For instance, predictive ultrasound
models developed by the International Ovarian Tumor Analysis (IOTA) consortium
are commonly used. However, they require training and expertise, making them
challenging to implement.
The predictive value of current serum biomarkers like CA-125 is limited, as it
does not increase in approximately 50% of early-stage ovarian carcinomas and
can also be elevated in benign gynecological conditions such as endometriosis.

Dutch guidelines use the Risk of Malignancy Index (RMI) to determine if the
risk of ovarian carcinoma is increased. This score is based on CA125
concentration, specific ultrasound features, and menopausal status. According
to Dutch guidelines, patients with an ovarian tumor are referred to oncology
centers if the RMI is elevated (>200). The published sensitivity and
specificity of the RMI in an unselected population of patients with ovarian
tumors are 72% and 92%, respectively. However, in the enriched population
treated in oncology centers, a pilot study among 366 patients revealed a
sensitivity of 84% for the RMI and a specificity of only 51%. This implies an
incidence of malignancy within this population of 40%, which is unacceptably
low, suggesting that half of the patients referred to oncology centers with
benign tumors undergo unnecessary extensive surgery and unnecessary emotional
distress about the possibility of cancer.

Tissue biopsies are crucial in treating ovarian carcinoma as they can confirm
or exclude malignancy preoperatively. However, in early stages, tissue biopsy
is considered an unwanted invasive procedure as it can cause the spread of
tumor cells. In summary, despite the development of various predictive models,
making an accurate preoperative diagnosis of early-stage ovarian carcinoma
remains challenging. There is an urgent need to develop predictive models with
a high degree of accuracy that are easy to implement in clinical practice to
maximize the number of malignant tumors treated in oncology centers.
Blood-based 'liquid' biopsies, or liquid biopsies, are emerging as an
alternative to traditional tissue biopsies, as they can provide accurate and
comprehensive information about tumors. Examples include circulating tumor DNA
(ctDNA), circulating tumor cells (CTC), and tumor-educated blood platelets
(TEPs). TEPs, responsible for hemostasis, can also absorb tumor signals in the
form of micro-tumor RNA. By using sequencing techniques such as DNA
methylation, low-coverage whole genome sequencing, and whole genome sequencing,
as well as detecting structural DNA and RNA changes in ctDNA and TEPs,
malignancies can be detected or excluded.

These DNA changes were first discovered incidentally through the non-invasive
prenatal test (NIPT). Besides assessing potential errors in fetal DNA, it was
found to detect DNA changes in maternal DNA; in asymptomatic pregnant women,
DNA changes were found in maternal DNA consistent with the presence of
malignancy. In a study of patients with early-stage ovarian carcinoma (stages I
and II), ctDNA analysis showed a sensitivity of 69% and a specificity of >99%.
Furthermore, it has been shown that the amount of ctDNA correlates with tumor
size. Other studies, albeit conducted within small patient populations, show
that when ctDNA is combined with existing tumor markers like CA-125, both
sensitivity and specificity increase.

In our small pilot study on TEPs, a sensitivity of 76% and specificity of 98%
were found for high-grade ovarian carcinoma, and a sensitivity of 81% and
specificity of 80% for low-grade carcinoma. Due to the limited size of this
pilot study on TEPs, a validation series will follow to determine if TEPs can
be added to the developing algorithm. Due to the small size of this pilot study
on TEP performance, the OVI-DETECT study will conduct a validation of TEPs as a
potential biomarker.

The primary objective of this study is to develop an diagnostic algorithm using
ct-DNA, and TEPs as liquid biomarkers in combination with the existing
ultrasound models (RMI and IOTA-models) and biomarkers (CA125 and HE4) to
differentiate between early ovarian cancer and benign ovarian tumors in
pre-operative setting.
Where we will first assess the TEPs in a validation series whether they will
become part of the algorithm.

Investigator-initiated, prospective case-control study.

There is no extra burden/risk for the patients in this study. Five extra blood
tubes are drawn at one time point during a standard pre-operative blood
sampling and 2 questionnaires have to be filled out.